CN1216678C - Capillary attration colloidal microball self-organization and two-dimensional, three-dimensional colloidal crystal preparing method - Google Patents

Abstract

The present invention relates to a colloidal microsphere self-organization under capillary attraction and a method for preparing two-dimensional colloidal crystal and three-dimensional colloidal crystal. A micro passage is arranged, so that a colloidal microsphere self-organization in the passage forms an ordered two-dimensional colloidal crystal and three-dimensional colloidal crystal by capillary attraction in the passage; the micro passage is a flaky passage. A cylindrical dielectric rod or a dielectric rod with a rectangular cross section is used and is placed between two smooth substrates in parallel to form a capillary passage. The present invention has no specific requirement to a peripheral atmosphere, has strong interference immunity and has no specific requirement to the concentration of a colloidal microsphere suspending liquid. The present invention has the advantages of simple technical process, short preparing period and high efficiency and can prepare single-domain two-dimensional colloidal crystal and single-domain three-dimensional colloidal crystal with large area, high quality and long-range order structure.

Description

Method for preparing two-dimensional and three-dimensional colloidal crystals by self-assembly of colloidal microspheres under capillary attraction

1. Technical field

The present invention relates to the self-organization of colloidal microspheres and the preparation of colloidal crystal materials, that is, the suspension of monodisperse polystyrene colloidal microspheres is sucked into the microchannel spontaneously through capillary attraction, and the self-assembly process in the microchannel A method for preparing two-dimensional and three-dimensional colloidal crystals.

2. Background technology

The study of two-dimensional and three-dimensional colloidal crystals composed of monodisperse submicron colloidal microspheres not only has important scientific research value, but also has important practical value. For example, it can be used as a template to prepare highly ordered porous ceramics, porous metals, and porous magnetic materials with specific functions. Using colloidal crystals as templates, introducing porous structures into bulk ceramics can greatly improve the strength of ceramics. In addition, because colloidal crystals have special optical diffraction characteristics and the existence of photonic band gaps, such materials can be used to prepare optical filters, optical switches, chemical and biological sensors, and optical integrated chips.

Generally, the size of colloidal microspheres is on the order of microns or submicrons. It is not only difficult but also inefficient to move the microspheres manually to arrange them into a three-dimensional close-packed structure. A variety of techniques exist to assemble colloidal microspheres into colloidal crystals. These preparation techniques often rely on the self-assembly process of colloidal microspheres under certain specific forces. To sum up, these methods can be divided into gravity-driven deposition, electrostatic repulsive self-organization, applied electric field-induced deposition, compression molding technology, vertical deposition technology and so on.

Figure 1A shows a schematic diagram of deposition purely under the action of a gravitational field, see K.E.Davis, W.B.Russel, W.J.Glantschnig, Sicence 1989, 245, 507. The obtained colloidal crystals often contain polycrystals with more point or plane defects, the thickness of the crystals is difficult to control, and the preparation cycle is longer. It is also not suitable for those colloidal microspheres whose gravity is greater than the buoyancy in suspension.

Electrostatic repulsion self-organization to obtain colloidal crystal assembly method is to rely on the electrostatic repulsion between charged microspheres to form an ordered structure, see N.Ise, Angew.Chem.Int.Ed.Engl.1986, 25, 323. In addition to requiring charged microspheres, this method requires strict control of the colloid concentration in the suspension, otherwise the result is likely to be a body-centered cubic, face-centered cubic, or mixed phase in a disordered phase. Like the gravity deposition method, this method is sensitive to perturbations.

The deposition induced by an external electric field requires a considerable amount of charges on the surface of the colloidal microspheres, and precise control of the strength of the electric field is required.

Figure 1B is a schematic diagram of compression molding technology, see Y.Xia, B.Gates, Y.Yin, Y.Lu, Adv.Mater.2002, 12 693. The advantage of this technique is that it can be applied to neutral spheres; it can obtain colloidal crystals with large area and controllable thickness; and there is no limit to the size of microspheres in principle. However, for microspheres with particularly small sizes, the difficulty increases correspondingly because the compression molding involves photolithography technology.

Figure 1C shows a schematic diagram of the vertical deposition method, see "Self assembly lights up," J.D. Joannopoulos, Nature, 2001, 414, 257. Compared with the previous techniques, it is easier to prepare large-area, high-quality single-domain colloidal crystals. However, this technology has particularly high requirements on the surrounding atmosphere and is also very sensitive to external disturbances. What can be obtained with a little perturbation is a colloidal crystal with a large number of defects and even local disorder.

3. Contents of the invention

The purpose of the present invention is to use the capillary suction to drive the suspension liquid into the microchannel; the colloidal microspheres at the top of the liquid surface in the microchannel self-organize to form an orderly arrangement inside the microchannel.

The present invention is provided with a tiny channel, so that the capillary in the channel attracts, so that the colloidal microspheres self-organize in the channel to form an ordered two-dimensional and three-dimensional colloidal crystal structure. The tiny channel is a lamellar channel.

In the invention, a spacer is placed between two flat sheets such as glass sheets to form a microchannel with the same thickness as the spacer; then one end of the microchannel is immersed in the suspension of colloidal microspheres. Evaporation of water within the microchannel occurs at its top. In order to compensate for the evaporated water in the tube, the suspension will be sucked into the tube from the lower end of the microchannel, which forms a water flow movement from bottom to top, and at the same time drives the colloidal microspheres to move to the top. After the colloidal microsphere reaches the top, its movement is restricted. These microspheres finally form a close-packed structure at the top of the microchannel according to the principle of the lowest system energy. After an appropriate time, the single-domain colloidal crystals of desired size can be prepared. Flat films are also like glass slides, book slides, etc.

The present invention is applicable to colloid microspheres of any size; it is applicable to charged and neutral colloid microspheres.

In the present invention, by controlling the thickness of the spacer in the microchannel, the thickness of the colloidal crystal can be precisely controlled very conveniently.

The diameter d of given colloidal microsphere among the present invention, composition colloidal crystal layer number N, in order not to grow out the colloidal crystal of layer number N+1 in microchannel, the thickness _H of microchannel must satisfy:

$<span\; class="notranslate">\; (</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 6</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; (</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 6</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; .</span>$

The invention has no special requirements on the surrounding atmosphere, strong anti-interference performance, and no special requirements on the concentration of the colloidal microsphere suspension.

The invention has the advantages of simple technical process, short preparation period and high efficiency, and can prepare large-area, high-quality colloidal crystals with single-domain two-dimensional and three-dimensional long-range ordered structures.

4. Description of drawings

Below in conjunction with accompanying drawing and by example the present invention will be further described:

Figure 1A shows a schematic diagram of deposition purely under the action of a gravitational field; Figure 1B shows a schematic diagram of the compression molding technique; Figure 1C shows a schematic diagram of a vertical deposition method. For details on these techniques, see the relevant literature.

Fig. 2 is a schematic diagram of the structural device of the present invention. Clamp 1, glass slide 2, spacer 3, container 4, colloid bead suspension 5, water flow direction 6 in the interlayer. The globules form an ordered sorting structure 7 at the upper end.

Fig. 3 is a scanning electron microscope (SEM) photograph of a local area of a two-dimensional colloidal crystal made of monodisperse polystyrene microspheres with a diameter of 1.5 microns according to the present invention.

Fig. 4 is an SEM photo of the edge region of the two-dimensional colloidal crystal made of monodisperse polystyrene microspheres with a diameter of 1.5 microns according to the present invention.

Fig. 5 is a SEM photograph of the surface of a three-dimensional colloidal crystal made of monodisperse polystyrene microspheres with a diameter of 650 nanometers according to the present invention.

Fig. 6 is a cross-sectional SEM photo of a three-dimensional colloidal crystal made of monodisperse polystyrene microspheres with a diameter of 650 nanometers according to the present invention.

Fig. 7 is a SEM photograph of the surface and cross-sectional morphology of a three-dimensional colloidal crystal made of monodisperse silica microspheres with a diameter of 500 nanometers according to the present invention.

5. Specific implementation

The invention prepares high-quality two-dimensional and three-dimensional colloidal crystals through the self-organization process of colloidal microspheres in microchannels under capillary attraction. The implementation method is shown in Figure 2. Photos are marked with size. It can grow polystyrene colloidal microspheres, silica colloidal microspheres and various composite dielectric colloidal microspheres.

The present invention first selects a wave plate as a substrate and lays it flat. Then two identical separators with a certain thickness are placed in parallel on the wave plate. Cover it with a wave plate of the same size. Finally, while maintaining the relative position of the two wave plates, fix them.

The separator in the present invention can be cylindrical or a dielectric rod with a rectangular cross section, as shown in FIG. 2 . The material of the spacer is selected from a dielectric material that can withstand a certain amount of extrusion without deformation. The clip 1 is used to fix the two glass slides 2, the spacer 3, and the container 4 to hold the colloid bead suspension 5. The direction of water flow in the compartment drives the small balls to move together, and the water starts to evaporate from the upper end of the slide, while the small balls form an orderly sorting structure on the upper end, and the water enters the interlayer from the lower end of the slide to compensate for the water evaporated from the upper end. At the same time, the pellets in the suspension were also brought into the compartment.

The present invention can also use monodisperse silica spheres as spacers. The distance between the two wave plates is equal to the diameter of the silica sphere.

In the invention, one end of the prepared microchannel is immersed in the configured colloidal microsphere suspension. After the colloids have grown to the desired size, the microchannels are lifted out of the suspension. Finally, large-area single-domain colloidal crystals are prepared.

In the present invention, the colloidal suspension is simultaneously stirred during the growth of the colloidal crystal, so as to prevent the deposition of the colloidal microspheres to the bottom of the suspension during the long-term growth of the crystal.

In the present invention, colloidal crystals are grown in microchannels formed between two relatively fixed substrates. Agitation of the suspension in the present invention does not affect crystal growth.

As an example of preparing two-dimensional colloidal crystals, silica spheres (1.8 microns in diameter) are used as spacers between two glass slides (1.6cm×2.5cm in size), and two clamps are used to clamp both sides of the slides , forming a microchannel with a thickness of 1.8 μm. Prepare 15 mL of colloidal microsphere suspension, put it into a crucible with a capacity of 20 mL, and carry out magnetic stirring. The polystyrene microspheres are 1.5 microns in diameter. The crystal growth time was 8 hours.

Fig. 3 is a SEM photograph of the middle local area of the two-dimensional colloidal crystal made of polystyrene microspheres with a diameter of 1.5 microns according to the present invention. Polystyrene microspheres are arranged in a highly ordered hexagonal close-packed structure.

Fig. 4 is an SEM photo of a local area at the edge of a two-dimensional colloidal crystal made of polystyrene microspheres with a diameter of 1.5 microns according to the present invention. It is confirmed from the figure that it is a single-layer, two-dimensional periodic ordered crystal.

As an example of preparing three-dimensional colloidal crystals, silica balls (1.8 microns in diameter) are used as spacers between two glass slides (1.6cm×2.5cm in size), and two clamps are used to clamp both sides of the slide, Form a microchannel with a thickness of 1.8 µm. Prepare 15 mL of colloidal microsphere suspension, put it into a crucible with a capacity of 20 mL, and carry out magnetic stirring. The polystyrene colloidal microspheres have a diameter of 650 nanometers. The crystal growth time was 12 hours.

Fig. 5 is the SEM photograph of the surface of the three-dimensional colloidal crystal made of polystyrene microspheres with a diameter of 650 nanometers in the present invention. It can be seen that the microspheres are arranged in an ordered structure on the surface.

Fig. 6 is the cross-sectional SEM observation result of the three-dimensional colloidal crystal made of polystyrene microspheres with a diameter of 650 nanometers. It can be seen that the crystal has three layers, and the arrangement on the cross-section is also long-range order, which proves the long-range order of the internal arrangement of the three-dimensional colloidal crystal prepared by the present invention.

As an example of preparing three-dimensional colloidal crystals, a spacer with a thickness of 9.0 μm was used between two glass slides (1.6 cm×2.5 cm in size) to form a microchannel. Fig. 7 is the surface and cross-sectional SEM observation results of the three-dimensional colloidal crystal made of silicon dioxide microspheres with a diameter of 500 nanometers. It can be seen that the crystal has 24 layers, and the long-range order on the section indicates the long-range order inside the three-dimensional colloidal crystal prepared by the present invention.

Claims (7)

1, the colloid micro ball self assembly under a kind of capillary attraction prepares the method for two dimension, three-dimensional colloidal crystal, it is characterized in that being provided with one by the capillary channel that constitutes width 500 nanometers-9 micron between two smooth substrates, capillary channel is immersed in the microballoon suspension, utilize the interior capillary force of passage that suspension is drawn in the capillary channel, colloidal crystal is grown by process of self-organization on the top of the inner fluid column of capillary channel, thereby the colloid micro ball self-organizing forms orderly two dimension, three-dimensional colloidal crystal structure in passage.

2, the method that is prepared the two and three dimensions colloidal crystal by the described self assembly of claim 1 is characterized in that adopting cylindrical or cross section is the dielectric rod of rectangle, parallelly is placed between two smooth substrates the capillary channel of formation.

3, the method that is prepared the two and three dimensions colloidal crystal by the described self assembly of claim 1 is characterized in that adopting single decentralized medium ball as sept, is placed between two smooth substrates, forms capillary channel.

4, the method that is prepared the two and three dimensions colloidal crystal by the described self assembly of claim 1 is characterized in that in crystal growing process the colloid micro ball suspension being stirred, and makes that the colloid concentration of suspension is in uniform state in the crystal growing process.

5, the method that is prepared the two and three dimensions colloidal crystal by claim 1 or 2 described self assemblies is characterized in that controlling by the thickness of regulating capillary channel the thickness of colloidal crystal.

6, the method for preparing the two and three dimensions colloidal crystal by claim 1 or 2 described self assemblies, the polystyrene colloid microballoon that it is characterized in that growing, silicon dioxide colloid microballoon and various composite dielectric body colloid micro ball.

7, the method that is prepared the two and three dimensions colloidal crystal by the described self assembly of claim 1 is characterized in that the number of plies N of microballoon in colloid micro ball diameter d, the colloidal crystal, the spacing H between composition two substrates capillaceous _NSatisfy:

$(\frac{\sqrt{6}}{3}(N-1)+1)d<H_N<(\frac{\sqrt{6}}{3}N+1)d.$

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